Surgical techniques and instruments have been developed which, among other things, reduce the size of incisions required to perform various surgical procedures. These techniques and instruments have been successful to various degrees. Indeed, surgical procedures which only a few years ago required an incision six or seven inches in length are today performed through incisions requiring less than one inch in length.
Trocars are one type of surgical instrument which have significantly contributed to these advances. In general, trocars are sharp pointed surgical instruments which can be used to create and maintain small, bowl like incisions in a body cavity. Surgical instruments, including miniaturized optical devices, can be inserted through these small incisions and manipulated to perform surgical procedures within the body cavity without ever exposing the patient's internal organs or structures to the outside environment. Thus, by enabling the creation and maintenance of small working holes within a patient's body wall, conventional trocars have greatly contributed to the reduction and size of the incisions required to perform surgical procedures and reduce the related complications.
Conventional trocars generally include an obturator and a cannula. An obturator is a small, nail like structure for penetrating the body wall to create a working channel into the body cavity. The cannula is a tube like structure which is inserted into the incision made by obturator to maintain a working channel even after the obturator is removed. In a typical scenario, the obturator and cannula are assembled into a single unit by inserting the obturator within the cannula and then a combination is used to puncture the body wall. The obturator can then be carefully withdrawn from the cannula without removing the cannula from the body wall. Surgical instruments can be inserted through this cannula to perform an entire surgical procedure within the body cavity as mentioned above.
In many surgical procedures involving trocars, the body cavity is inflated with a non toxic gas before the trocar is employed to create a working pocket or volume within the patient and to prevent the trocar from penetrating internal organs during insertion. For example in an appendectomy, a patient's abdomen is inflated with a gas through a veress needle. The obturator is then used to place cannulas in various locations throughout the inflated abdomen to perform the procedure. One such cannula would typically be used to pass a small camera and light into the body cavity so the surgeon could view the operating area within the patient. Other cannulas would be used at other locations to pass surgical instruments into the cavity and remove tissue such as the appendix from the patient.
It is important to maintain the abdomen of the patient in an inflated state throughout this procedure. To this end, conventional cannulas are often provided with the sealing flap valves or the like which prevent the gas from escaping from the patient's abdomen after the obturator has been withdrawn. However these sealing valves do not prevent gas leakage when surgical instruments having a diameter which is smaller than the diameter of the cannula is employed. Instead gas can easily pass through the gap between the inner walls of the cannula and the outer surface of the surgical instrument to deflate the work area. To prevent such deflation of this type from occurring, physicians often are required to utilize only those instruments whose dimensions closely match those of the cannula. This requirement apparently limits the surgeon's freedom of choice in selecting surgical instruments for the procedure. Thus, while a surgeon's instrument might be preferred by a physician, the physician might nonetheless be forced to use a less preferred, and possibly less effective, tool to perform a procedure to avoid deflating a body cavity.